HK1112900A - Method for producing olefin oxides and peroxides, reactor and the use thereof - Google Patents

Description

Process for the preparation of olefin oxides and peroxides, reactor and use thereof

Technical Field

The invention relates to a method for producing olefin oxides, in particular propylene oxide, and peroxides by heterogeneously catalyzed gas phase oxidation in a wall reactor, and to the use of a particularly suitable reactor for the gas phase oxidation.

Background

The epoxidation of olefins, such as propylene, using oxygen in the liquid phase and in the gas phase is known.

DE 19748481 a1 describes static micromixers and microreactors having a specific micrometric shape and their use for preparing ethylene oxide in the gas phase by catalytic oxidation of unsaturated compounds with the aid of air or oxygen.

The epoxidation of olefins, such as propene, with hydrogen peroxide in the liquid phase or in the gas phase is a newer process variant.

For example, U.S. Pat. No. 3, 5,874,596 and DE-A-19731627 describe processes for the epoxidation of olefins in the liquid phase using A titanium silicalite (silikalite) catalyst. A disadvantage of this process is the rapid deactivation of the catalyst due to high-boiling by-products.

The use of wall reactors, more precisely microreactors, for the oxidation of organic compounds in the liquid phase is known from EP-A-903,174. Here, use is made of cooled microreactors in which the heat generated by the exothermic oxidation reaction with the peroxide can be dissipated in an accelerated manner. By reaction control at moderate temperatures, the decomposition of liquid peroxides can be kept at a low level.

US-A-4,374,260 discloses A process for the epoxidation of ethylene in the gas phase at 200-300 ℃ using A silver containing catalyst. The epoxidizing agent used is air or molecular oxygen.

Further epoxidation of reactants in the gas phase is known from US-A-5,618,954, wherein 3, 4-epoxy-1-butene is reacted with an oxygen-containing gas over A silver-containing catalyst in A fixed bed reactor at A temperature of 100-400 ℃ in the presence of water.

It has also been attempted to epoxidize lower olefins in the gas phase with hydrogen peroxide which is thermally or catalytically activated (see g.m. mamedjarov and t.m. nagiev in azerb. khim. zh. (1981), 57-60, and t.m. nagiev et al in Neftekhimiya31(1991), 670-. The disadvantage is the high reaction temperatures which prevent an economical process.

Another method uses a Si-containing catalyst and a reaction temperature of 425 ℃ and 500 ℃ (see H.M. Gusenov et al, Azerb. Khim. zh. (1984), 47-51). Here, a tubular reactor is used and the propylene conversion is from 15 to 65%.

Yet another approach uses a Fe-containing catalyst (see T.M. Nagiev et al, Neftekhimiya31(1991), 670-. The reaction yield is about 30% and the catalyst has a very short working life. Longer working life and further reduction of reaction temperature Fe in combination with alumina as support can be used^IIIOH-protoporphyrin catalyst. When this catalyst is used, at a temperature and C of about 160 deg.C₃H₆∶H₂O₂∶H₂A propylene oxide yield of about 50% was obtained at a feed molar ratio of 1: 0.2: 0.8.

In the gas phase₂-C₆An improved process for the epoxidation of olefins is described in DE-A-10002514. The reaction is carried out using gaseous hydrogen peroxide in the presence of the catalyst selected. Fixed bed and fluidized bed reactors are mentioned as suitable reactors. According to this document, the reaction is carried out at a temperature of less than 250 ℃, preferably from 60 to 150 ℃, and the olefin is used in equimolar amounts, preferably in excess.

In wall reactors, more precisely microreactors, using H₂O₂Processes for carrying out the gas-phase epoxidation of propene are known. For example, Kruppa and Schulth have investigated epoxidation reactions in terms of reaction technology also in microreactors (IMRET 7, 2003).

In Chemie Ingenieur Technik 2004, 76(5), 620-5, G.Markowz et al describe the gas phase epoxidation of propylene to propylene oxide using vaporous hydrogen peroxide over a titanium silicalite catalyst in a microreactor. Details concerning reactor design and industrial reaction conditions are not disclosed.

Disclosure of Invention

Starting from this prior art, it was an object of the present invention to provide an improved process for the catalytic gas-phase epoxidation of olefins by means of peroxides, in which a high space-time yield is achieved with respect to industrial use and at the same time a high selectivity for the conversion of thermally unstable valuable materials into products is achieved. At the same time, another object of the present invention is an improved process for the preparation of peroxides.

It has surprisingly been found that when using a wall reactor with catalyst content in which at least one dimension of the reaction space is kept in the range of less than 1cm and the inner wall is coated with a specific material, the product selectivity of the peroxide oxidizing agent increases at increased reaction temperatures in comparison with conventional fixed-bed reactors, and thereby a higher selectivity of the peroxide oxidizing agent used is confirmed. It has furthermore been found that the peroxides surprisingly also have an increased stability in this particular reactor, so that these reactors are also suitable for the synthesis of peroxides.

It is a further object of the invention to provide a reactor which is particularly suitable for gas phase reactions with peroxides and for gas phase reactions with the formation of peroxides.

The present invention provides a process for preparing an olefin oxide by heterogeneously catalyzed gas-phase epoxidation of an olefin with a peroxide in the presence of water and, optionally, an inert gas, which process comprises the following measures:

i) the gas-phase epoxidation is carried out at a temperature above 100 c,

ii) using a reactor having at least one reaction space, at least one dimension of which is less than 10mm,

iii) wherein the surface of the reaction space has a layer comprising aluminum oxide, zirconium oxide, tantalum oxide, silicon dioxide, tin oxide, glass and/or enamel, and

iv) wherein the reaction space comprises a catalyst, preferably coated or partially coated with a catalyst.

For carrying out the process according to the invention, all wall reactors or microreactors known per se can be used. Within the context of the present specification, wall reactors are those in which at least one of the dimensions of the reaction space or spaces is/are less than 10mm, preferably less than 1mm, particularly preferably less than 0.5 mm.

The catalyst content of the reaction space or spaces may also extend to the collecting space or distributor space, wherein also catalyst contents different from the reaction space may be present.

The reactor may have one reaction space or, preferably, a plurality of reaction spaces, more preferably a plurality of reaction spaces running parallel to one another.

The dimensioning of the reaction space can be arbitrary, provided that at least one dimension varies within a range of less than 10 mm.

The reaction space may have a circular, oval, triangular or polygonal, in particular rectangular or square, cross-section. The dimension or one of its dimensions of the cross section is preferably less than 10mm, i.e. at least one side length or the diameter or one diameter is preferably less than 10 mm.

In a particularly preferred embodiment, the cross section is rectangular or circular and has only one dimension, i.e. the side length or the diameter, which varies in the range of less than 10 mm.

The material of construction of the reactor may be any as long as it is stable under the reaction conditions, allows sufficient heat dissipation and the surface of the reaction space is completely or partially coated with the above-mentioned specific material.

In this way, the reactor can be made of a metallic material, but here its reaction space or spaces are coated with aluminum oxide, zirconium oxide, tantalum oxide, silicon dioxide, tin oxide, glass and/or enamel.

The typical proportion of the total amount of the mentioned oxides and/or glasses in the surface layer of the reaction space is 20-100 wt.%, based on the material forming the surface layer of the reaction space.

In a particularly preferred embodiment, the reactor or at least the part surrounding the reaction space consists of aluminum or an aluminum alloy. It is well known that this material oxidizes in the presence of a hydrogen peroxide compound to form alumina.

A further feature of the reactor used according to the invention is that the reaction space contains completely or partly the catalyst. Preferably the surface of the reaction space is partially or completely coated with catalyst.

The catalyst may be coated onto a specific surface of the substrate or the reaction space may be completely or partially filled with finely divided, supported or unsupported catalyst. The volumes packed or coated with catalyst are porous and permeable to the reactants under the reaction conditions in the reactor, so that these can also be in contact with the specific material.

It has surprisingly been shown that when using the specific materials mentioned under the reaction conditions, the selectivity of the desired reaction increases with increasing temperature, thereby increasing the product yield of the peroxide used or produced.

The present invention therefore also provides a process for preparing peroxides by heterogeneously catalyzed gas-phase reaction, which process comprises the following measures:

v) reacting the peroxide precursor with oxygen and/or an oxygen-containing compound at a temperature above 100 ℃ to form a peroxide,

vi) using a reactor having at least one reaction space with at least one dimension of less than 10mm,

vii) wherein the surface of the reaction space has a layer comprising aluminum oxide, zirconium oxide, tantalum oxide, silicon dioxide, tin oxide, glass and/or enamel, and

viii) wherein the reaction space optionally comprises a catalyst, preferably coated or partially coated with a catalyst.

The precursor of the peroxide is usually oxygen. The invention therefore comprises a process for the preparation of hydrogen peroxide from hydrogen and oxygen in a specific reactor. It is also possible to react organic molecules with hydrogen peroxide to produce organic peroxides, such as peracetic acid.

The present invention also provides a reactor for reactions employing peroxides or generating peroxides, comprising:

a) at least one reaction space, at least one dimension of which is less than 10mm,

b) the surface of the reaction space has a layer comprising aluminum oxide, zirconium oxide, tantalum oxide, silicon dioxide, tin oxide, glass and/or enamel, and

c) the reaction space contains a catalyst, preferably the surface of the reaction space is coated or partially coated with a catalyst.

The invention further provides for the use of the specifically coated reactor for gas phase oxidation with peroxides or for the synthesis of peroxides, in particular for heterogeneously catalyzed gas phase reactions.

In a particularly preferred embodiment of the process according to the invention, the gas-phase epoxidation is carried out in a microreactor which has a plurality of spaces arranged in parallel in a vertical or horizontal manner, which spaces have at least one inlet duct and one outlet duct, wherein the spaces are formed by stacked plates or layers and a part of the spaces is at least one reaction space having a dimension of less than 10mm, the other part of the spaces is a heat transfer space, wherein the inlet ducts to the reaction space are connected to at least two distributor units and the outlet ducts of the reaction space are connected to at least one collection unit, wherein the heat transfer between the reaction space and the heat transfer space takes place via at least one common space wall, which common space wall (raumwind) is formed by a common plate.

A microreactor of this type, which is particularly preferably used, is arranged in all the spaces with spacer elements, contains catalyst material which is applied at least partially on the inner wall of the reaction space, has a hydraulic diameter in the reaction space of less than 4000 μm, preferably less than 1500 μm, particularly preferably less than 500 μm, which is defined as the quotient of four times the area of the free flow cross section and the circumference, and has a ratio between the vertical minimum distance between two adjacent spacer elements and the slot height of the reaction space after coating with catalyst of less than 800 and greater than or equal to 10, preferably less than 450, particularly preferably less than 100.

As olefins, it is possible to use all compounds having one or more double bonds. Straight or branched and cyclic olefins may be used. The olefins may also be used as mixtures.

The olefinic starting material has at least two carbon atoms. Olefins having any number of carbon atoms may be used provided that they are sufficiently thermally stable under gas phase epoxidation conditions.

Preference is given to using olefins having from 2 to 6 carbon atoms. Examples are ethylene, propylene, 1-butene, 2-butene, isobutene, and pentenes and hexenes, including cyclohexene and cyclopentene, or mixtures of two or more of these olefins, as well as higher olefins. The process is particularly preferably suitable for preparing propylene oxide from propylene.

As peroxides, it is possible to use H₂O₂Hydroperoxide or any hydrocarbon group containing organic peroxide, provided that they are sufficiently thermally stable under the gas phase reaction conditions.

As hydrogen peroxide, all compounds containing H can be used₂O₂The vaporizable composition of (a). Advantageously, an aqueous solution is used which contains 30 to 90 wt.% hydrogen peroxide, which is evaporated and fed into the wall reactor. The gaseous hydrogen peroxide is obtained by evaporation in an apparatus suitable for this purpose. To reduce subsequent reactions with evaporated water from aqueous hydrogen peroxide, it is preferred to concentrate the H highly₂O₂The solution was fed to an evaporator. Thereby also reducing energy consumption.

As the catalyst, any catalyst for gas phase oxidation of olefin with hydrogen peroxide can be used.

One class of suitable and preferred catalysts are molecular sieves, especially synthetic zeolites. Particularly preferred catalysts from the series of molecular sieves are based on the general formula (SiO)₂)_1-x(TiO₂)_xSuch as titanium silicalite-1 (TS1) having an MFI crystal structure, titanium silicalite-2 (TS-2) having an MEL crystal structure, titanium-beta-zeolite having a BEA crystal structure, and zeolite ZSM 48Titanium silicalite-48 of crystal structure. TiO of TS-1₂The content is preferably 2 to 4%. Titanium silicalite is commercially available. It is also possible to use a titanium silicalite which, in addition to the titanium silicalite, also contains amorphous or crystalline oxides such as SiO₂、TiO₂、Al₂O₃And/or ZrO₂Instead of pure titanium silicalite.

The crystallites of the titanium silicalite can be distributed uniformly together with the crystallites of the other oxides and form particles or lie as shells on cores made of the other oxides.

Another class are metal organic catalysts, such as iron organic (protoporphyrin) or titanium organic compounds on a suitable support.

Another class of catalysts which are preferably used are preferably inorganic compounds, in particular oxides, which comprise one or more elements of transition groups 4 to 6 of the periodic Table of the elements and/or arsenic and/or selenium compounds as catalytically active component.

Particularly preferred are compounds of titanium, vanadium, chromium, molybdenum and tungsten.

The catalytic action of these compounds is believed to be activation of the peroxide starting material by the porous structure of the catalyst and/or by the ability of the catalyst to reversibly generate a peroxy compound, although other mechanisms are not excluded.

Examples of particularly suitable catalysts are vanadium oxide, vanadates and their H₂O₂An adduct.

Another particularly suitable class of epoxidation catalysts comprises molybdenum or tungsten. An example is MoO₃And WO₃Molybdic and tungstic acids, alkali and alkaline earth molybdates and tungstates, provided that their basicity does not lead to hydrolysis of the epoxide, homomolybdates, homopolytungstates, heteropolymolybdates and heteropolytungstates (═ homopolyacids and heteropolyacids) and H of the mentioned substance classes₂O₂Adducts, such as peroxomolybdic acid, peroxotungstic acid, peroxomolybdate and peroxotungstate, which can also be generated in situ during epoxidation from other Mo and W compoundsAnd (4) obtaining.

Catalysts for preparing hydrogen peroxide are, for example, on suitable supports, for example on carbon or on SiO₂Gold, palladium or other noble metals. Generally, no catalyst is required for the preparation of the organic peroxide.

To produce a particularly suitable coating, the catalyst is applied to a part or all of the walls of the reaction space together with a binder which is inert with respect to the epoxidation reaction. One particular challenge is the property of the binder to be as inert as possible with respect to the gaseous peroxide.

There are many examples of non-reactive binders used in liquid applications. However, the majority of the substances show a clear difference in their catalytic decomposition performance with respect to gaseous peroxides. The use of coatings comprising alumina, silica or silicates has proven to be particularly preferred. These preferred catalytic coatings can be prepared as follows: the non-reactive binder is mixed with the active ingredient, preferably in powder form, shaped and heat treated (Tempern).

In another embodiment, a catalyst is used whose active components have been applied to a porous support. In this way, particularly large internal volumes may be produced, which leads to particularly high reaction yields.

The starting materials for the process of the invention are fed into a wall reactor. The feed stream may comprise other components, such as steam and/or other inert gases.

The process is generally carried out continuously.

It is important that no liquid phase is formed in the wall reactor, i.e. during the reaction over the catalyst. Thereby increasing the operating life of the catalyst and reducing the consumption for the regeneration process.

In addition, other gases, such as low-boiling organic solvents, ammonia or molecular oxygen, can also be added to the raw gas mixture.

The olefin to be epoxidized can in principle be used in any proportion to the peroxide component, preferably hydrogen peroxide.

In general, an increased olefin and peroxide component, preferably H, is employed₂O₂The feed molar ratio of (a) to (b) achieves an improved epoxide yield. Preferably wherein the olefin is present in excess, preferably in a feed molar ratio of olefin to peroxide component of from 1.1: 1 to 30: 1.

The gas phase reaction is carried out at a temperature above 100 c, preferably above 140 c. The preferred reaction temperature is 140-700 deg.C, especially 140-250 deg.C.

The gas-phase reaction is advantageously carried out at a pressure in the range from 0.05 to 4MPa, preferably from 0.1 to 0.6 MPa.

The reaction mixture can be worked up in a manner known to the person skilled in the art.

The process of the invention is distinguished by a high selectivity for the valuable oxidizing agent, simple reaction control and a high space-time yield.

In the case of particularly preferred microreactors, special auxiliary devices for preventing explosions can be dispensed with.

Detailed Description

The following examples illustrate the invention without limiting it.

All experiments were carried out in an apparatus consisting of an evaporator and a microreactor in which the hydraulically effective diameter is less than 1mm and which is made of aluminum. A commercially available stabilized hydrogen peroxide solution with a concentration of 50 wt% and a different catalyst were used. The measurement and metering of the gas streams (propylene, nitrogen) and of the hydrogen peroxide solution were carried out using mass flow sensors from the company Bronkhorst.

A50% strength by weight hydrogen peroxide solution and a gas mixture of propene and nitrogen which has been preheated to the evaporator temperature are metered into the glassIn a glass evaporator (100 ℃). The gas mixture leaving the evaporator consisted of 18ml/minH₂O₂53ml/min propylene, 247ml/min N₂And water fractions and reacted in microreactors at various temperatures within 100-180 ℃. For this purpose, the reactor was coated with 0.3g of titanium silicalite-1 catalyst.

Surprisingly, an increasing selectivity of the valuable oxidant to propylene oxide with increasing temperature was measured in the microreactor. The results are shown in the table below. The selectivity increased by 100% as the reaction temperature increased from 100 ℃ to 140 ℃.

Reaction temperature (. degree.C.)	100	120	140	160	180
						PO selectivity (%) of oxidizing agent	15	27	32	33	37

Kruppa, Amal and Schulth have investigated the temperature pairing using H in a fixed-bed reactor made of glass₂O₂Gas phase heterogeneously catalyzed propylene on titanium silicalite-1Effect of epoxidation (Europacat IV, 2003). The results are shown in the table below. Reacted H as expected in practice₂O₂The PO selectivity of (a) continuously decreases with increasing reaction temperature. The selectivity decreased by 15% as the reaction temperature increased from 100 ℃ to 140 ℃.

Reaction temperature (. degree.C.)	100	120	140	150
					PO selectivity (%) of oxidizing agent	14	13	12	12

Thus, in the epoxidation in microreactors, an increase in the selectivity to propylene oxide of the oxidant and an increase in the space-time yield can be achieved simultaneously with an increase in temperature in comparison with the known prior art. This effect cannot be achieved in a conventional fixed bed reactor having a hydraulic effective diameter of 1 cm. Accordingly, the hydraulically effective diameter, which is critical for this effect, is less than 1 cm.

Claims (22)

1. Process for the preparation of an olefin oxide by heterogeneously catalyzed gas-phase epoxidation of an olefin with a peroxide, which process comprises the following measures:

i) the gas-phase epoxidation is carried out at a temperature above 100 c,

ii) using a reactor having at least one reaction space, at least one dimension of which is less than 10mm,

iii) wherein the surface of the reaction space has a layer comprising aluminum oxide, zirconium oxide, tantalum oxide, silicon dioxide, tin oxide, glass and/or enamel, and

iv) wherein the reaction space comprises a catalyst.

2. The process according to claim 1, characterized in that a reactor is used in which the reaction space is coated or partially coated with a catalyst.

3. Process according to claim 1, characterized in that an olefin having 2 to 6 carbon atoms, preferably propene, is used as olefin and H₂O₂Used as a peroxide.

4. The process according to claim 1, characterized in that the reactor has a plurality of reaction spaces which run parallel to one another, the reaction spaces each having at least one, preferably only one, dimension which is less than 1mm, in particular less than 0.5 mm.

5. Process according to claim 4, characterized in that the gas-phase epoxidation is carried out in a microreactor having a plurality of spaces arranged in parallel in a vertical or horizontal manner, which spaces each have at least one inlet duct and one outlet duct, wherein the spaces are formed by stacked plates or layers and one part of the spaces is a reaction space and the other part of the spaces is a heat transfer space, wherein the inlet ducts to the reaction space are connected to at least two distributor units and the outlet ducts of the reaction space are connected to at least one collection unit, wherein the heat transfer between the reaction space and the heat transfer space takes place via at least one common space wall, which common space wall is formed by a common plate.

6. Process according to claim 5, characterized in that the microreactor is arranged with spacer elements in all spaces, a catalyst material being applied at least partially to the inner walls of the reaction space, wherein the hydraulic diameter, defined in the reaction space as the quotient of four times the area of the free flow cross-section divided by the circumference, is less than 4000 μm, and the ratio between the vertical minimum distance between two adjacent spacer elements and the slit height of the reaction space after coating with catalyst is less than 800 and greater than or equal to 10.

7. A process according to claim 1, characterized in that an element of sub-groups 4 to 6 of the periodic Table of the elements and/or a compound of arsenic or selenium and/or a molecular sieve is used as catalyst.

8. Process according to claim 7, characterized in that a titanium-containing zeolite, especially TiO₂Titanium silicalite-1 (TS-1) in an amount of 2-4% was used as the catalyst.

9. A process according to claim 1, characterized in that a metallo-organic compound, especially a ferro-organic or a titano-organic compound, is used as catalyst.

10. Process according to claim 7, characterized in that an oxide of vanadium or a molybdenum or tungsten compound selected from the group consisting of oxides, acids, molybdates, tungstates, homo-or heteropolyacids containing molybdenum or tungsten and H's of these classes is used as catalyst₂O₂An adduct.

11. The process according to claim 1, characterized in that a catalyst is used whose active components have been applied to a porous support.

12. A method according to claim 1, characterized in that the catalyst is present on the surface of the reaction space applied together with a binder which is inert with respect to the epoxidation reaction.

13. A method according to claim 12, characterized in that the inert binder consists essentially of alumina, silica or silicates.

14. The process according to claim 1, characterized in that the gas-phase epoxidation is carried out at a temperature of 140-700 ℃, preferably 140-250 ℃.

15. The process according to claim 1, characterized in that the gaseous mixture comprising olefin and peroxide is contacted at a pressure of 0.05 to 4 MPa.

16. The process according to claim 1, characterized in that the gas mixture comprising olefin and peroxide is used in a molar ratio of more than 1: 1, preferably from 1.1: 1 to 30: 1.

17. Process for the preparation of peroxides by heterogeneously catalyzed reaction in the gas phase, which process comprises the following measures:

v) carrying out the reaction at a temperature above 100 ℃ by reacting a peroxide precursor with oxygen and/or an oxygen-containing compound to form a peroxide,

vi) using a reactor having at least one reaction space with at least one dimension of less than 10mm,

vii) wherein the surface of the reaction space has a layer comprising aluminum oxide, zirconium oxide, tantalum oxide, silicon dioxide, tin oxide, glass and/or enamel, and

viii) wherein the reaction space optionally comprises a catalyst.

18. A reactor for reactions employing peroxides or generating peroxides, comprising:

a) at least one reaction space, at least one dimension of which is less than 10mm,

b) the reaction space surface has, partially or completely, a layer comprising aluminum oxide, zirconium oxide, tantalum oxide, silicon dioxide, tin oxide, glass and/or enamel, and

c) the reaction space contains a catalyst.

19. Reactor according to claim 18, characterised in that the surfaces of the reaction space are coated or partly coated with a catalyst.

20. Reactor according to claim 18, characterised in that at least one dimension of the reaction space is less than 1mm, particularly preferably less than 0.5 mm.

21. Use of a reactor according to any of claims 18-20 for gas phase oxidation with peroxide.

22. Use of a reactor according to any of claims 18-20 for the synthesis of peroxides.